PropertyArrayView.h

#pragma once
 
#include "CesiumGltf/PropertyType.h"
#include "getOffsetFromOffsetsBuffer.h"
 
#include <CesiumUtility/SpanHelper.h>
 
#include <gsl/span>
 
#include <cstddef>
#include <cstring>
#include <variant>
#include <vector>
 
namespace CesiumGltf {
 
template <typename ElementType> class PropertyArrayView {
public:
  PropertyArrayView() : _values{} {}
 
  PropertyArrayView(const gsl::span<const std::byte>& buffer) noexcept
      : _values{CesiumUtility::reintepretCastSpan<const ElementType>(buffer)} {}
 
  const ElementType& operator[](int64_t index) const noexcept {
    return this->_values[index];
  }
 
  int64_t size() const noexcept { return this->_values.size(); }
 
  auto begin() { return this->_values.begin(); }
  auto end() { return this->_values.end(); }
  auto begin() const { return this->_values.begin(); }
  auto end() const { return this->_values.end(); }
 
private:
  gsl::span<const ElementType> _values;
};
 
template <typename ElementType> class PropertyArrayCopy {
public:
  PropertyArrayCopy() : _storage{}, _view() {}
 
  PropertyArrayCopy(const std::vector<ElementType>& values) noexcept
      : _storage(), _view() {
    size_t numberOfElements = values.size();
    size_t sizeInBytes = numberOfElements * sizeof(ElementType);
    this->_storage.resize(sizeInBytes);
    std::memcpy(
        this->_storage.data(),
        reinterpret_cast<const std::byte*>(values.data()),
        sizeInBytes);
    this->_view = PropertyArrayView<ElementType>(this->_storage);
  }
 
  PropertyArrayCopy(PropertyArrayCopy&&) = default;
  PropertyArrayCopy& operator=(PropertyArrayCopy&&) = default;
 
  PropertyArrayCopy(std::vector<std::byte>&& buffer) noexcept
      : _storage(std::move(buffer)), _view(this->_storage) {}
 
  PropertyArrayCopy(const PropertyArrayCopy& rhs)
      : _storage(rhs._storage), _view(this->_storage) {}
 
  PropertyArrayCopy& operator=(const PropertyArrayCopy& rhs) {
    this->_storage = rhs._storage;
    this->_view = PropertyArrayView<ElementType>(this->_storage);
    return *this;
  }
 
  const ElementType& operator[](int64_t index) const noexcept {
    return this->_view[index];
  }
 
  int64_t size() const noexcept { return this->_view.size(); }
 
  auto begin() { return this->_view.begin(); }
  auto end() { return this->_view.end(); }
  auto begin() const { return this->_view.begin(); }
  auto end() const { return this->_view.end(); }
 
  const PropertyArrayView<ElementType>& view() const { return this->_view; }
 
  PropertyArrayView<ElementType>
  toViewAndExternalBuffer(std::vector<std::byte>& outBuffer) && {
    outBuffer = std::move(this->_storage);
    PropertyArrayView<ElementType> result = std::move(this->_view);
    this->_view = PropertyArrayView<ElementType>();
    return result;
  }
 
private:
  std::vector<std::byte> _storage;
  PropertyArrayView<ElementType> _view;
};
 
template <> class PropertyArrayView<bool> {
public:
  PropertyArrayView() : _values{}, _bitOffset{0}, _size{0} {}
 
  PropertyArrayView(
      const gsl::span<const std::byte>& buffer,
      int64_t bitOffset,
      int64_t size) noexcept
      : _values{buffer}, _bitOffset{bitOffset}, _size{size} {}
 
  bool operator[](int64_t index) const noexcept {
    index += _bitOffset;
    const int64_t byteIndex = index / 8;
    const int64_t bitIndex = index % 8;
    const int bitValue = static_cast<int>(_values[byteIndex] >> bitIndex) & 1;
    return bitValue == 1;
  }
 
  int64_t size() const noexcept { return _size; }
 
private:
  gsl::span<const std::byte> _values;
  int64_t _bitOffset;
  int64_t _size;
};
 
template <> class PropertyArrayView<std::string_view> {
public:
  PropertyArrayView()
      : _values{},
        _stringOffsets{},
        _stringOffsetType{PropertyComponentType::None},
        _size{0} {}
 
  PropertyArrayView(
      const gsl::span<const std::byte>& values,
      const gsl::span<const std::byte>& stringOffsets,
      PropertyComponentType stringOffsetType,
      int64_t size) noexcept
      : _values{values},
        _stringOffsets{stringOffsets},
        _stringOffsetType{stringOffsetType},
        _size{size} {}
 
  std::string_view operator[](int64_t index) const noexcept {
    const size_t currentOffset =
        getOffsetFromOffsetsBuffer(index, _stringOffsets, _stringOffsetType);
    const size_t nextOffset = getOffsetFromOffsetsBuffer(
        index + 1,
        _stringOffsets,
        _stringOffsetType);
    return std::string_view(
        reinterpret_cast<const char*>(_values.data() + currentOffset),
        (nextOffset - currentOffset));
  }
 
  int64_t size() const noexcept { return _size; }
 
private:
  gsl::span<const std::byte> _values;
  gsl::span<const std::byte> _stringOffsets;
  PropertyComponentType _stringOffsetType;
  int64_t _size;
};
 
template <typename T>
bool operator==(
    const PropertyArrayView<T>& lhs,
    const PropertyArrayView<T>& rhs) {
  int64_t size = lhs.size();
  if (size != rhs.size()) {
    return false;
  }
 
  for (int64_t i = 0; i < size; ++i) {
    if (lhs[i] != rhs[i]) {
      return false;
    }
  }
 
  return true;
}
 
template <typename T>
bool operator==(
    const PropertyArrayView<T>& lhs,
    const PropertyArrayCopy<T>& rhs) {
  return lhs == PropertyArrayView(rhs);
}
 
template <typename T>
bool operator==(
    const PropertyArrayCopy<T>& lhs,
    const PropertyArrayView<T>& rhs) {
  return lhs.view() == rhs;
}
 
template <typename T>
bool operator==(
    const PropertyArrayCopy<T>& lhs,
    const PropertyArrayCopy<T>& rhs) {
  return lhs.view() == rhs.view();
}
 
template <typename T>
bool operator!=(
    const PropertyArrayView<T>& lhs,
    const PropertyArrayView<T>& rhs) {
  return !(lhs == rhs);
}
 
template <typename T>
bool operator!=(
    const PropertyArrayView<T>& lhs,
    const PropertyArrayCopy<T>& rhs) {
  return !(lhs == rhs);
}
 
template <typename T>
bool operator!=(
    const PropertyArrayCopy<T>& lhs,
    const PropertyArrayView<T>& rhs) {
  return !(lhs == rhs);
}
 
template <typename T>
bool operator!=(
    const PropertyArrayCopy<T>& lhs,
    const PropertyArrayCopy<T>& rhs) {
  return !(lhs == rhs);
}
 
} // namespace CesiumGltf